Time-element device and motor-control system employing the same



y 9, 1929- G. B. STARIE 1.720.613

TIME ELEMENT DEVICE AND MOTOR CONTROL SYSTEM EMPLOYING THE SAME OriginalFiled May 4, 1925 Fig. I.

. George B. fitarie, D65 I Hmrneg.

Patented an 9, 1929.

U -lTED STATES PATET orric GEORGE E. STABIE, OF BOHENECTADY, NEW YORK,ASSIGNOB 1'0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

'I'IEE-ELEHENT DEVICE AND MOTOR-CONTROL SYQTEE EMPLOYEE THE .1;

Application filed Kay 4, 1925, Serial K0. 28,038. Renewed January 24,18%.

My invention relates to an improved electro-responsive time elementdevice for general purposes, and in particular to an electromagnetictime element device for controlling the 5 operation of motor controllingswitch alter the operation of another motor controlling switch.

My invention also relates to an improvedmotor control system employingthe'im roved time element device of the invention or obtaining thedesired succession of operation of motor controlling switches orcontactors with a desired time interval interposed between the operationof successively operated contactors.

The present application is directed to improvements of and is covered ba copending application of Eu ene R. Caric iofi and Benjamin W. Jones,erial No. 527,520, filed Jan.

6, 1922, a renewal of an application, Serial No. 354,030, filed Jan. 26,1920. I

Time element control of electromagnetic switches, as heretoforeproposed, has left something to be desired in the way of a simplc,reliable and effective device which invariably gives the desired timeinterval of operation. Motor control systems operating on the timeelement principle, as heretofore proposed, have also left something tobe desired in that complications are introduced which render the systemuncertain in opera- .tion.

' In carrying my invention into efiect, I employ an electromagnetic timeelement device of very simple construction, and one which when employedin a motor control system, for example, makespossible a very simple,efiective and reliable s tern for producing the intended control 0 themotor. The electromagnetic time element switch is provided with amagnetic structure with a winding thereon and a magnetic movable elementarmature carrying a switch contact, the armature being biased to theunattracted position and the switch contact carried by the armaturebeing biased to a definite position, as for example, the closedposition. 'The armature of the electromagnetic time element device isbiased to the unattracted position by any suitable means such as aspring, the tension of which may be adjusted so that when the arms--ture is in the attracted position, it is ma netically held inthat sitionagainst t e action of the spring tending to move the armature to theunattracted position. The winding of the electromagnet is connected soas to be shunted when a previously operated switch is closed. Byreason-of the fact that the winding has a considerable inductive efiect,the short-circuitmg of the winding will perhill; the induced current tomaintain a magnctic flux in the magnetic structure of the electromagnetand thus maintain the armature in the attracted position for anappreciable interval of time. The winding is provided with a suthcientnumber of turns so that with the armature in the attracted position, thema etic flux of the relay will be considerably in excess of thatrequired to hold the armature in the attracted position thus insuringthat the time interval introduced will not be appreciably affected bysuch variables as variations of the supply circuit potential orvariations of the heating of the winding. Adjustment of the timeelementis obtained by adjusting the air gap between the armature and thecore of the electromagnet, and this is preferably done by mounting ashim of non-magnetic material on the armature so that when the armatureis magneticall operated to the attracted position, the slum will insurethat there will be a definite and invariable air ga between the armatureand the pole face. he time interval may be very accurately ad'ustcd tothe desired value by employing a im'of the correct thickness for theparticular time interval desired. The time interval is also adjusted byvarying the tension of the spring which biases the armature to theunattracted position, since the time interval is obtained by the pull ofthe induced flux of the electromag'net overpowering the strain of thespring tendin to move the armature to the unattracted position. Thead'ustment obtained .by varying the strain 0 the sprin is (Luiteaccurate and is simpl obtaine so t at as a practical matter, a ter asuitable thickness of shim has been determined, the principal adjustmentwill be by var ing the spring tensionjgi; I

or a better understanding of the Invention, reference is had theaccompanying drawin in which Fig. 1 1s a very simple dragram 0 a timeelement motor control system n accordance with the invention Fig. 2 is aside view of an electromagnetic time element relay in accordance withthe invention, and Fi 3 is a front view of thesame. fieferri first toFigs. 2 and seen that t e time element switch or relay 3 it will be.

no j

comprises an electromagnet structure including the strap of magneticmaterial 10 and the core 11 of magnetic material on which the windingspool 12 is mounted. The strap 10 and the core 11 are secured in anysuitable manner to an insulating supporting base, as for example, bmeans of the bolt 13. The magnetic mova le element or armature 14 of thedevice is pivotally mounted with respect to the strap 10 and is biasedto the unattracted position by means of the spring 15. This spring ismounted on a bolt 16, which is carried by the support 17 secured to thestrap 10.

The nut 18 is provided for adjusting the tension of the spring 15 andthus varying the time interval of operation of the device. The shim 19of non-magnetic material is secured to the inner face of the armature 14so as to make abutting engagement with the end of the pole face 11 whenthe armature is in the attracted position, thus introducing a definiteand invariable air gap between the armature and the pole when thearmature is in the attracted position.

The armature carries a contact 20 at its lower end thereof, and thiscontact is arranged to make engagement with the stationary andadjustable contact 21. The contact 21 is carried by means of a strap ofelectrical conducting material 22, which is secured to the insulatingsupport by means of the bolt 23. The arrangement is such that a singlewinding on the electromagnetic device controls the entire operationthereof and this winding has a sufiicient number of turns so that withthe armature in the attracted position the magnetic flux of theelectromagnet is considerably in excess of that required to maintain thearmature in the attracted position. When the winding 12 isshort-circuited, the inductive efi'ect of the electromagnet is employedto maintain. the armature in the attracted position .for an appreciableinterval of time, and

by reason of the fact that the holding flux was considerably in excessof that required to maintain the armature in the attracted position,this time interval will not be a preciably affected by the variableswhich a. cot previous time element devices, namely, variations of thesupply circuit potential and variations of the heating of the winding.

In Fig. 1, the electric motor having an armature 24 and a series fieldwinding 25 is arranged to be connected to the direct current supplycircuit 26 by means of the pair of directional contactors 27 and 28 forthe forward direction of motor operation and the pair of directionalcontactors 29 and 30 for the reverse direction of motor operation. Theline contactor 31 is provided for opening the motor circuit upon failureof power and the connections are such that .the master controller 32must be returned to the off or neutral position in order to reclose thiscontactor. The current taken by the motor is limited by means ofresistance in the motor armature contactor 34 and the acceleratingIGSIStOIS' 35 and 36 controlled by the accelerating contactors 37 and38, respectively. The plugging contactor 34 is under the control of aplugging relay 39. This relay is intended primarily to delay theenergization of the plugging contactor 34 upon a rapid reversal'of themotor by the well-known plugging action, aI 1 d the relay is providedwith a winding 40 for determining the sequence of the closing of theplugging contactor 34 with reference to other parts of the system. Thewinding 41 is connected across the resistors 33 to 36 so as to give acurrent limit control for this relay.

The accelerating resistor contactor 37 is controlled by means of thetime element relay 42, of the construction shown in more detail in Figs.2 and 3. In general it may be said that this relay is provided forgiving a time interval of operation after the closing of the pluggingcontactor 34, dependent practically entirely onthe inductive efiect ofthe relay when the winding of the relay is shunted in response to theshunting of the plugging resistor 33. s

As thus constructed and arranged, and with the parts in their respectivepositions indicated in Fig. 1, the operation of the system is asfollows: The disconnecting switch 43 in the main motor circuits, and thedisconnecting switch 44 in the control circuits will first be closed.The closing of the disconnecting switch 44 will cause the line contactor31 to be energized to close, the circuit being from the positive supplyconductor, segment 45 of the mastercontroller 32 and segment 46 of thiscontroller, through the winding of contactor 31 to the negative supplyconductor. The line contactor 31 in closing, will also close theauxiliary switch 47, thereby establishing a maintaining circuit for theline contactor and permitting the master controller to be moved out ofthe off position without affecting the energization of the linecontactor.

It will also be observed that when the disconnecting switch 44 isclosed, the winding of the relay 42 will be energized across the supplycircuit with the resistor 48 in series with the relay winding, and thatthe winding 40 of the relay 39 will also be energized across the supplycircuit with the resistor 49 in series with the relay windingJ These tworelays will thereforebe energized to open their respective contacts,preparatory to later operating to produce the intended control of themotor. If now the master controller 32 is thrown to the fullrunningposition forward (the master controller thrown to the left finalposition), the directional contactors 27 and 28 will first be closed,thereby connecting the motor to the source of supply for forwarddirection of motor operation, the coils of contactors 27 and 28 beingenergized through the segments 46 and 50 of the mas ter controller. Thedirectional contactor 27 will close its auxiliary contacts 51 and thusshunt the winding 40 of the relay 39 so as to place this relay under thecontrol of the winding 41 which is now energized responsively to thevoltage drop across the resistors 33 to 36 inclusive. The closing of thedirectional contactor 28 will simultaneously close the auxiliary switchcontacts 52, thereby partially completing a circuit for the winding ofthe plugging contactor 34, the circuit being from the negative supplyconductor, winding of contactor 34, segments 53 and 54 or the mastercontroller 32, to the contacts of the relay 39, but since these contactsare temporarily at least maintained open, the closing of the auxiliaryswitch contacts 52 will not effect the energization of the pluggingcontactor 34. However, as soon as the motor current has dropped to thepredetermined value, the winding 41 of relay 39 will be unable to holdthe relay contacts in their open position against the strain of thespring 55 and this relay Will close, energizing the plugging contactor34 to close through the circuit previously traced and the segments and46 of the master controller and the auxiliary switch 47 to the positivesupply conductor.

When the plugging contactor closes, it also closes its auxiliary switchcontacts 56, thereby shunting the winding of relay 42. As previouslyexplained, this relay is of the construction illustrated in more detailin Figs.

2 and 3. Although the relay winding has been shunted, the relay will notrelease its armature for an appreciable interval of time, due solely tothe inductive effect of the relay winding. When the magnetic holdingeffect of the flux of the induced current is overpowered by the biasingspring of the relay, the relay will very quickl close its contacts,thereby energizin the winding of the resistor contactor 37 t rough acircuit from the negative suppl conductor, contacts of relay 42, winding0 contactor 37, segment 57 of master switch 32, segment 54 of the'masterswitch, contacts of relay 39, auxiliary switch 52, segments 50 and 46 ofthe master switch auxiliary switch 47 to the positive sup ly conductor.Contactor 37 in closing also 0 oses its auxiliary contacts 58, therebyenergizingthe resistor contactor 38 to close. The resistor 36 willordinarily be of comparatively small value as compared to the resistors35 'and 33 so that the time interval of operation of the closin of thecontactor 38 after the contactor 37 wi be suflicient for certainapplications.

thrown to the full reverse position, since those skilled in the art willreadily under-.

from an understanding of the operation whenv full reversal is had.

When themaster controller moves out of its third operative forwardposition, the accelerating contactors 37 and 38 are directly deenergizedand opened and when the master controller moves out of its secondoperative position forward, the plugging contactor 34 will bedeenergized and opened. The introduction of the resistance in the motorarmature circuit will cause the winding 41 oi the relay 39 to he againmomentarily energized in accordance with the drop in potential acrossthe resistors 33 to 36-, inclusive, and the opening of the auxiliaryswitch 56will remove the shunt about the winding of relay 42 so thatrelays 42 and 39 will both open. The relay 39 willhave a further openingeffect applied thereto by the energization of the winding 40 in responseto the opening of the auxiliary switch contacts 51 of directionalcontactor 27 when the master controller is moved out of its firstoperative forward position to the neutral position, It may be said atthis time that while the above stated operation has been assumed to betaking place at a certain definite sequence, this has been done merelyfor the purpose of explanation of what could be the case but which isnot necessarily in all cases the lexact sc uence, since if the mastercontro ler is t rown very quickly from the full forward position to thefull reverse position, the opening of the resistor cont-actors, thedirectional contactors and the opening of the relays 42 and 39 will bealmost simultaneous.

When the master controller reaches the first reverse position, thedirectional contactors 29 and 30 will be closed, and the Winding 40 ofthe relay 39 will be shunted through the auxiliary contacts 59 of thecontactor 29. The relay 39 will not close its contacts until the currentin the motor armature circuit has decreased to a redetermined value, atwhich time the windlng 41 is sufiiciently reduced in energization sothat the relay may close. The closing of the plugging contactor 34 as aresult of the closing of the relay 39 will effect the shunting of thewinding of the relay 42 as before, and this relay will introduce thesame time interval etween the operation of the plugging contactor 34andthe acceleratin contactor 39, as was previouslythe case i or forwardmotor operation. The accelerating contactor 38 Wlll close promptly afterthe closing of the contactor 37 in the manner previously explained.

It will be observed that I have provided a ve simple and effective timeelement relay which de ends for its time of operation on the invariabletime required for the holding effect of the fiuxof therelay when thewinding of the relay is shunted. The operation of the relay contact fromand to the closed position is entirely under the control of the flux setup by the winding of the relay. The-relay is of itself a very simple,effective and reliable ,device, and one which can be manufactured inlarge scale production for a materially lower cost than other timeelement devices with which I am familiar. The provision of the simple,effective and reliable adjusting devices of the relay afford meanswhereby the time interval may be very accurately adjusted to the exacttime desired, and as before stated, this determined time interval willbe invariable for all practical purposes. This electromagnetic timeelement relay is covered in a divisional application, Serial No.125,112, filed J uly'26, 1926. It will also be observed that the controlsystem in which I employ the time interval relay for obtaining thedesired time interval of operation between the closing of the pluggingcontactor 34 and the accelerating contactor 37 is very simple, thustending toward a great reliability of operation.

What I claim as new and desire to secure byLetters Patent'of the UnitedStates, is:

' 1. In combination, a motor controlling switch, a motor controllingresistor, a contactor for shunting the resistor, and a normally closedelectromagnetic time element relay for controlling said contactor tocontrol the shunting of the resistor a definite interval of time afterthe closing of said switch, the winding of said relay being connected tobe shunted at the same time that the said switch is closed and the timeelement of operation of the relay being effected solely by theinductance of the relay.

2. In combination, two motor controlling contactors, an electromagnetictime elementrelay for delaying the energization of the second of saidcontactors for an interval of time after the closing of the first ofsaid contactors, the said relay having a winding which is connected tobe energized to open the relay quickly against its bias to the closedposition when the first contactor is open and to be shunted when thefirst contactor closes, the operation of said relay to the closedposition and the time interval introduced thereby to the closed positionbeing determined solely by the inductance of the relay.

3. In combination, in a system of motor control, a pair of directionalswitches, a plugging resistor,-a contactor for, shunting said resistor,a single relay for controlling the in moving from the open.

closing of the pluggi n contactor the said relay having two win ingswhich cooperate to open the relay andhold the same in the.

open position, one of said windings being connected to be energized whensaid directional switches are open and to be shunted by the closing ofeither of said directional switches, and the other of said windingsbeing connect-ed to regulate the closing of the relay in accordance withthe motor current, a time interval after the shunting of said firstwinding.

4. In combination, in a system of motor control, a pair of directionalswitches, a plugging resistor and an accelerating resistor, a contactorfor shunting each of said resistors, a single plugging relay forcontrolling the closing of the plugging contactor, the said relay havingtwo windings, which cooperate to open and hold the relay in the openposi tion, one of: said windings bein connected to be energized whensaid directlonal switches are opened and to be shunted by the closing ofeither of said directional switches, the said other relay winding beingconnected to regulate the closing of the relay in accordance with themotor current an interval of time after the closing of eitherdirectional switch, and a single winding normally closed time elementrelay for controlling said accelerating contactor, the winding of saidaccelerating relay being connected to be energized to open said relaywhen said directional switches are open and to be shunted by the closingof said plugging contactor to delay the closing of the re- I lay andtheclosing of the accelerating contactor for a definite interval of timeafter the closing of the plugging contactor.

5. In combination, two motor controlling switching mechanisms, thesecond switching solely by the inductance of said winding is introducedin the closing of the second switching mechanism in accordance with itsbias. a

In witness whereof, I have hereunto set my hand this 2nd day of May,1925.

GEORGE B. STARIE.

